Grinstead-Snell-Probability · Problem 7.1.8

Sums of Random Variables

Mathematics · sums-discrete-random-variables-convolution

Problem

A baseball player is to play in the World Series. Based upon his season play, you estimate that if he comes to bat four times in a game the number of hits he will get has a distribution pX=(01234.4.2.2.1.1).p_X = \begin{pmatrix} 0 & 1 & 2 & 3 & 4 \\ .4 & .2 & .2 & .1 & .1 \end{pmatrix}. Assume that the player comes to bat four times in each game of the series. (a) Let XX denote the number of hits that he gets in a series. Using the program NFoldConvolution, find the distribution of XX for each of the possible series lengths: four-game, five-game, six-game, seven-game. (b) Using one of the distributions found in part (a), find the probability that his batting average exceeds .400 in a four-game series. (The batting average is the number of hits divided by the number of times at bat.) (c) Given the distribution pXp_X, what is his long-term batting average?

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